The polarizing forces I have described throughout this book are acting on both coalitions. So why has the Democratic Party weathered them in a way the Republican Party hasn’t? Why are the two parties so different? The answer is twofold: Democrats have an immune system of diversity and democracy. The Republican Party doesn’t. This has not left the Democrats unaffected by the forces of polarization, to be sure. But if polarization has given the Democratic Party the flu, the Republican Party has caught pneumonia.
